1. Field of the Invention
The invention relates primarily to the reduction of NO.sub.x in exhaust gases at low temperature with the use of catalysts.
2. Description of the Prior Art
DE-PS 27 43 031 describes catalysts of the prior art for the removal of nitrogen oxides in exhaust gases, which are based on metal phthalocyanines, whereby the exhaust gases are treated at temperatures above 250.degree. C. with NO or O.sub.2. DE-AS 26 39 848 also describes a process for nitrogen oxide reduction in exhaust gases by means of the addition of NH.sub.3, whereby an oxide catalyst consisting essentially of hematite crystals with a defined crystal lattice is used. The above-mentioned patent is incorporated herein by reference as if the contents thereof were set forth herein in their entirety.
Generally, for the elimination of nitrogen oxides, NO.sub.x, in exhaust gases with the use of catalysts, ammonia gas NH.sub.3 is fed in, whereupon the nitrogen oxide reacts with the ammonia, forming nitrogen and water at temperatures of generally 350.degree. C. to 550.degree. C. on the catalyst surface.